The deportation of 95-year-old Nazi camp guard Jakiw Palij Monday was a significant development in the ongoing effort to rectify the errors that may have let thousands of war criminals flood into the United States. in the wake of World War II, according to the former director of the Department of Justice office designated with handling those cases.

“The Holocaust was the greatest crime in history and there’s no point at which we can say, ‘Okay, let’s just forget about it,’” said Allan Ryan, who served as the first director of the Department of Justice Office of Special Investigations from 1980 to 1983 and is now an attorney at Harvard University.

This is the first deportation of a suspected Nazi since John Demjanjuk was sent back to Germany in 2009. He was prosecuted there for being an accessory to 28,000 murders, but he died while appealing his conviction.

A federal judge stripped Palij of his U.S. citizenship 15 years ago, but the effort to remove him stalled when Germany, Poland, and Ukraine refused to accept him. For years, he was widely known to be living on a quiet street in Queens, his life occasionally interrupted by reporters seeking comments or protesters demanding justice.

“The United States expresses its deep appreciation to the Federal Republic of Germany for re-admitting former Nazi slave-labor camp guard Jakiw Palij, who was removed from the United States on August 20,” State Department spokeswoman Heather Nauert said in a statement Tuesday.

During a telephone briefing Tuesday, U.S. Ambassador to Germany Richard Grenell told reporters he presented a moral argument to German officials rather than a legal one, convincing them they have an obligation to take Palij because he was acting in the name of the German government.

“I think one of the issues that had been the reason for stalling is because the previous approach had been trying to work through the legal argument,” Grenell said.

According to the Justice Department, Palij was an armed guard at the Trawniki labor camp in 1943 when thousands of Jewish prisoners in occupied Poland were slaughtered. He is not accused of participating in those killings, but he did prevent prisoners from escaping. Palij was later believed to be among the Trawniki-trained guards who served in the Deployment Company and the Streibel Battalion, units that participated in violent operations in 1944 and 1945.

In 1949, Palij applied to immigrate to the U.S. under the Displaced Persons Act, falsely claiming that he worked on his father’s farm and in a German factory during the war. In 1957, he became a naturalized U.S. citizen.

According to The Associated Press, Palij first came to investigators’ attention in the early 1990s when his name appeared in an old Nazi roster and another former guard revealed he was living somewhere in the U.S. In 2002, the Justice Department filed a complaint seeking to revoke his citizenship. A federal judge granted that request in 2003, and he was ordered deported in 2004. That is when things got complicated.

The Polish village where Palij lived is now in Ukraine, and he is not a German citizen. All three countries refused to take him. His deportation order languished for over a decade without much progress.

Palij admitted being a guard at Trawniki and lying on his visa application, but he denied participating in war crimes. His attorney has not commented on his removal.

A renewed public push to drive Palij out of the country began last fall, with New York senators and state lawmakers urging the State Department and Department of Justice to act. According to Grenell, getting Germany to take Palij was a top priority for President Trump when he was appointed, and Monday’s action was the result of weeks of diplomatic negotiations with the new German government.

“We brought it up very regularly, and as loudly as we could, on a regular basis, with every person that we met,” Grenell told reporters. “Regardless of what the issue was, we brought up this case. And there just seemed to be a new energy with the new government here in Germany, and we’re very thankful for their help.”

At 95 years old and in poor health, Palij is unlikely to face prosecution in Germany, and officials there have indicated they lack evidence to prove his culpability for war crimes. He landed in Duesseldorf early Tuesday and was expected to be taken to a care facility in the town of Ahlen.

“Today’s removal sends yet another message of deterrence to anyone who would dare even contemplate participating in human rights crimes, namely that the passage of time, even many decades, will never weaken our government’s resolve to pursue justice on behalf of the victims,” said Eli Rosenbaum, of the Department of Justice Human Rights and Special Prosecutions Section.

"The United States officials involved in this case, and especially OSI Director Eli M. Rosenbaum, deserve enormous credit for their unflagging efforts to have Palij removed from the United States,” Efraim Zuroff of the Simon Wiesenthal Center said in a statement. “A 14-year long campaign has finally been crowned with success. Trawniki guards do not deserve the privilege of living in the United States and that was finally achieved last night."

New York Assemblyman Dov Hikind, who spearheaded the effort by state legislators to pressure the Justice Department over Palij last year, credited President Trump for delivering “long-overdue justice.”

“I have remained with this issue for 14 years because Palij’s presence here mocked the memory of the millions who perished,” Hikind said in a statement. “There was no question of his guilt. It was imperative that someone responsible for Nazi atrocities be held accountable for his crimes. While his victims can no longer seek justice, I am delighted that President Trump and his administration took it upon themselves to deliver justice.”

Even some frequent Trump critics welcomed the news.

“Nazi prison guards have no place in the USA. We must stand firmly against hate, anti-Semitism and bigotry in all its forms. Good riddance to this war criminal,” Senate Minority Leader Chuck Schumer tweeted.

Palij was the last Nazi war criminal in the U.S. who was under a deportation order, but he was almost certainly not the last Nazi war criminal left in the country. There are believed to be thousands of others, an unfortunate artifact of flawed 1940s immigration reforms intended to selectively address the 1.5 million people displaced by World War II.

“In the years after the war, the U.S. was not particularly receptive to letting Holocaust survivors in but wanted to show it was trying to do something about the problem of displaced persons,” said Barry Trachtenberg, author of “The United States and the Nazi Holocaust: Race, Refuge, and Remembrance” and director of Jewish studies at Wake Forest University.

According to Trachtenberg, opposition from anti-Semitic elements in Congress blocked significant action to help those impacted by the Holocaust. The result was the Displaced Persons Act, which President Harry Truman reluctantly signed in 1948 despite calling it “flagrantly discriminatory” and stating it “mocks the American tradition of fair play.”

The legislation streamlined admission for certain broad categories of people displaced by the war and by Soviet occupation, making it easy for Nazis to slip in claiming to be farmers from Eastern Europe without much scrutiny.

“That was very much a political decision made by the Congress after the war to take in all these people who were fleeing communism,” Ryan said.

Decades later, lawmakers began to realize how sloppy the admissions process was and how freely visas had been handed out. The discovery that so little was done to verify claims at the time is what led to the creation of the Office of Special Investigations in 1979.

In 2010, the OSI became part of the DOJ Human Rights and Special Prosecution Section.

“It was set up because in the late 1970s, the then-congresswoman from Brooklyn, Elizabeth Holtzman, became very interested in the topic of Nazi war criminals in the U.S.,” Ryan said.

Holtzman held hearings on the issue and helped pass legislation to establish an office within the Department of Justice dedicated to investigating and denaturalizing suspected Nazis.

Much of the work, Ryan said, began with searches of contemporary records, like the rosters on which Palij was listed. Investigators compared those names and dates of birth with people living in the U.S., and if there was a match, they needed to determine if the person played a verifiable role in any atrocities that would justify deporting them.

“What we had to prove in order to persuade a federal judge to strip citizenship was not simply that they lied on their papers. We had to prove they were Nazi war criminals,” Ryan said.

Since DOJ created the OSI, federal prosecutors have initiated proceedings against 137 suspected Nazis, 67 of whom have been removed from the country by deportation, extradition or voluntary departure. Twenty-eight died while their cases were pending, and nine others died in the U.S. after they were ordered deported.

According to Ryan, refusal by Germany and other nations to accept deported Nazis has been a problem from the start. While he was head of OSI, he traveled to West Germany and attempted to convince the minister of justice there that the country should accept responsibility even for Nazis who were not German citizens.

“He looked at me and he said, ‘Mr. Ryan, who wants to import America’s Nazi war criminals?’” he recalled.

Officials have found more cooperation over the years. In 2017, Poland sought the extradition of Michael Karkoc, a 99-year-old Minnesota man believed to be a Ukrainian-born SS commander. Earlier this year, the U.S. reportedly asked medical experts to determine if he is competent to stand trial and travel.

Any other suspected Nazis would be of similar age and likely similar health to Palij, if they are still alive, and proceedings begun against them now could drag on for years, but experts say the assumption that they will all be dead soon is no reason not to pursue justice.

“The time to do that was in 1948 when they came here. The time that it was actually done was 1980 and the years beyond. The time when it should be done now is now. When we started in 1980, the reaction from a lot of people was, ‘Oh my god, those guys are so old,’” Ryan said, noting that Palij was in his late 50s at that time.

Acting against alleged Nazi war criminals regardless of their age or the complexity of the cases carries symbolic and educational significance, even if they are never shipped off to Europe.

“It has to be done, I think not only for the Jewish community but for humanity as a whole,” Trachtenberg said, “because we still live in an age where genocide occurs No one should ever feel they can get away with such actions, even after generations.”